Guide

6
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Base Resistance –
 Has a finite base resistance which, depending on geometry and design, can be as low as
100 Ω and as high as 500 KΩ.
 Its base (flat state) resistance is adjusted by changing the active geometry of the sensor
– doubling the length will double the resistance or doubling the width halves the base
resistance. Another method for adjusting base resistance is to add a conductive pattern
over the sensor area to reduce the resistance.
 It is important to remember that when used in a voltage divider network the fixed
resistor should be as close to the geometric mean of the actuated sensor and the base
resistance of the sensor as possible. The easiest way to use the Bend Sensor
®
Device is
by installing it as part of a voltage divider network. Other processors have made the
voltage divider unnecessary being able to connect the sensor directly to a constant
current DAC. Refer to the Bend Sensor
®
Technology Electronics Interface Design
Guide for more information.
Radius of Curvature –
 When wrapped around a mandrel of a given diameter, for any given arc length, the
resistance can increase by more than 10 times. It is dependent on the mandrel diameter,
or in other words, the radius of curvature of the Bend Sensor
®
Device.
 The smaller the radius of curvature the sharper the bend, and therefore, the greater the
rate and magnitude of increase in the resistance of the Bend Sensor
®
Device.
 Many factors, such as the geometry of the printed coating, the base substrate thickness,
the type of overlaminate that is used, and the method of actuation will also affect the
amount of the increase in resistance.
Specifications:
Test set up – 0.28” x 1.00” sensor wrapped around a 3/8” diameter mandrel using a
0.005” thick polyimide substrate.
Base Resistance: 2,000 Ω ± 25%
Resistance while wrapped around mandrel: 140k Ω ± 25%
 Once again, the base resistance, rate of change, and total change are affected by coating
geometry, substrate thickness, type of overlaminate used, and method of actuation. It is
best to test the Bend Sensor in your actual application to get accurate data for your
design.